1. Field of the Invention
The present invention relates to a method for bonding a pair of substrates. Further, the present invention relates to a method for manufacturing a sealing structure. Further, the present invention relates to a method for manufacturing a light-emitting device.
2. Description of the Related Art
A technique is known in which two substrates are attached and bonded to each other with glass (hereinafter also referred as a glass layer) obtained by melting or sintering glass frit containing low-melting-point glass as a main component. Further, a technique in which a highly airtight sealing structure is formed using the bonding technique of substrates is known. In a technique disclosed in Patent Document 1, a paste containing a binder and glass frit (referred to as a “frit material” in the document) including low-melting glass as a main component is applied to a glass substrate along an edge of the glass substrate, the binder is removed and the glass frit is melted to form a glass layer (referred to as a “frit glass” in the document) by baking of the paste, and the glass layer is irradiated with laser light with the glass substrate overlapping with a counter substrate so that the glass layer is welded to the counter substrate; thus, a highly airtight sealing structure is formed.
Since such a glass layer has a high gas barrier property, a sealed space can be kept away from the external atmosphere. A method of sealing using such a glass layer can be preferably used for a device employing an element, such as an organic EL (electroluminescent) element or an organic transistor, whose performance is rapidly impaired once the element is exposed to air (including moisture or oxygen).
Examples of the device employing an organic EL element are a lighting device using an organic EL element as a light source, an image display device in which a thin film transistor and an organic EL element are combined, and the like. Since the organic EL element can be formed into a film and a large-area organic EL element can be easily formed, a lighting device including a planar light source can be provided using the organic EL element. In addition, an image display device using an organic EL element needs no backlight which is necessary for a liquid crystal display device and the like, and accordingly, a thin, lightweight, and high contrast display device capable of driving with low power consumption can be achieved.